Gearless motorized conveyor roller

Abstract

The drive roller of this invention utilizes a brushless D.C. motor which has a stator or armature mounted on a fixed shaft which directly drives a permanent magnet rotor mounted inside a roller tube. A variable frequency drive supplies three-phase power to a Y-connected three phase winding which is composed of three groups of two coils. Thus twelve electromagnets are formed which drive the permanent magnet rotor which has sixteen poles. The brushless D.C. motor is of a modular design and can be easily built in one inch length increments to supply one lb-in of torque for each one-inch increment. The variable frequency controller operates at a relatively low frequency of 15-75 Hz. Hall effect sensors are used to provide feedback on motor speed and position. The armature laminations making up the brushless D.C. motor core are also relatively thick because of the relatively low power necessary to drive the motor and the resultant relatively low eddy currents present in the motor core. For a motor with a 4.0 lb-in design torque and a rotor and stator length of four inches, the current draw will be approximately 0.8 amps consuming about 15 Watts of power.

I claim:  
     
       1. A drive roller and roller controller for a roller conveyor comprising: 
       a shaft rigidly mounted to a conveyor support:  
       a stator having a core and plurality of windings on the core, the windings producing a plurality of magnetic poles when energized the stator being mounted about the shaft;  
       a roller tube surrounding the shaft and the stator, the roller tube having an interior a first end and a second end, and an exterior surface having a diameter of about 1.9 inches;  
       a first tube closure mounted to the roller tube first end, and a second tube closure mounted to the roller tube second end, the tube closures being rotatable mounted on the shaft to rotatable mount the roller tube on the shaft;  
       a permanent magnet rotor having a plurality of poles which alternate North and South the rotor being fixedly mounted to the roller tube interior and overlying and coaxial with the stator, the rotor and the stator forming a brushless three-phase motor, with the rotor and the fixedly mounted roller tube being driven by changes in induced magnetic fields in the stator; and  
       a variable frequency controller in power supplying connection to the windings of the stator for controlling the rotation speed of the rotor, wherein the permanent magnet rotor is constructed of a plurality of cylindrical segments, each segment constructed of ferromagnetic particles embedded in a flexible matrix, and wherein the plurality of poles is imposed on said cylindrical segment.  
     
     
       2. The apparatus of claim  1  wherein the cylindrical segments have alignment means for aligning the plurality of poles imposed on each segment. 
     
     
       3. The apparatus of claim  1  wherein the ferromagnetic particles are composed of an alloy of NdFeB. 
     
     
       4. The apparatus of claim  1  wherein the ratio between the permanent magnetic poles and the number of poles produced by energizing the windings of the stator is 4:3. 
     
     
       5. A drive roller and roller controller for a roller conveyor comprising: 
       a shaft rigidly mounted to a conveyor support;  
       a stator having a core and plurality of windings on the core, the windings producing a plurality of magnetic poles when energized the stator being mounted about the shaft;  
       a roller tube surrounding the shaft and the stator, the roller tube having an interior a first end and a second end, and an exterior surface having a diameter of about 1.9 inches;  
       a first tube closure mounted to the roller tube first end, and a second tube closure mounted to the roller tube second end, the tube closures being rotatably mounted on the shaft to rotatably mount the roller tube on the shaft:  
       a permanent magnet rotor having a plurality of poles which alternate North and South, the rotor being fixedly mounted to the roller tube interior and overlying and coaxial with the stator, the rotor and the stator forming a brushless three-phase motor, with the rotor and the fixedly mounted roller tube being driven by changes in induced magnetic fields in the stator; and  
       a variable frequency controller in power supplying connection to the windings of the stator for controlling the rotation speed of the rotor, wherein six windings are employed on the stator and are arranged to induce twelve poles when energized.  
     
     
       6. A roller conveyor system comprising: 
       a frame;  
       a multiplicity of idler rollers positioned for rotation on the frame;  
       a plurality of drive rollers positioned on the frame, each drive roller having a shaft fixed against rotation to the conveyor frame; a stator having a core and at least three windings on the core, the stator being mounted about the shaft, the stator mounted about the rigid shaft; a roller tube surrounding the shaft and the stator, and having a first and a second end and an interior; two tube closures, one tube closure rigidly mounted to each of the first end and the second end of the roller tube, wherein the tube closures are rotatably mounted on the shaft, to rotatably mount the roller tube on the shaft; and a permanent magnet rotor having a plurality of poles, the rotor fixedly mounted to the roller tube interior and overlying and coaxial with the stator, the permanent magnet rotor and the stator forming a brushless three-phase D.C. motor, with the rotor and connected roller tube being driven by changes in induced magnetic fields in the stator, and a sensor means mounted to the stator for determining angular velocity of the rotor;  
       a plurality of variable frequency three-phase power supply controllers for controlling the rotation speed of each drive roller, each variable frequency controller connected to one of said multiplicity of drive rollers for controlling the rotation speed of the connected drive roller rotor; and  
       a programmable controller operably connected to the variable frequency controllers to control the speed of all the drive rotors.  
     
     
       7. The roller conveyor system of claim  6  wherein the permanent magnetic rotor is constructed of a plurality of cylindrical segments, each segment constructed of ferromagnetic particles embedded in a flexible matrix, and wherein the plurality of poles is imposed on said cylindrical segment. 
     
     
       8. The roller conveyor system of claim  7  wherein the cylindrical segments have alignment means for aligning the plurality of poles imposed on each segment. 
     
     
       9. The roller conveyor system of claim  7  wherein the ferromagnetic particles are composed of an alloy of NdFeB. 
     
     
       10. The roller conveyor system of claim  6  wherein the ratio between the permanent magnetic poles and the number of poles produced by energizing the windings of the stator have a ratio of 4:3. 
     
     
       11. The roller conveyor system of claim  6  wherein six windings are employed on the stator and are arranged to induce twelve poles when energized. 
     
     
       12. The roller conveyor system of claim  6  wherein the roller tube has an exterior surface having a diameter of about 1.9 inches. 
     
     
       13. The roller conveyor system of claim  6  wherein the shaft has a extension which is slidably mounted on the shaft and biased in an extended position by a spring.